rssh, scponly: Unrestricted command execution
— GLSA 200412-01

rssh and scponly do not filter command-line options that can be exploited
to execute any command, thereby allowing a remote user to completely bypass
the restricted shell.

Affected Packages

Package

net-misc/scponly on all architectures

Affected versions

< 4.0

Unaffected versions

>= 4.0

Package

app-shells/rssh on all architectures

Affected versions

<= 2.2.2

Unaffected versions

>= 2.2.3

Background

rssh and scponly are two restricted shells, allowing only a few
predefined commands. They are often used as a complement to OpenSSH to
provide access to remote users without providing any remote execution
privileges.

Description

Jason Wies discovered that when receiving an authorized command from an
authorized user, rssh and scponly do not filter command-line options
that can be used to execute any command on the target host.

Impact

Using a malicious command, it is possible for a remote authenticated
user to execute any command (or upload and execute any file) on the
target machine with user rights, effectively bypassing any restriction
of scponly or rssh.